Make the Pastry: In a large bowl, rub the cold, cubed butter into the flour with your fingertips until the mixture resembles fine breadcrumbs. Stir in the 50g of caster sugar. Add the beaten egg and 1 tablespoon of cold water, and mix with a knife until the dough starts to come together. Use your hands to gently form a ball, adding the second tablespoon of water only if it seems too dry. Wrap in cling film and chill in the fridge for at least 30 minutes.

Blind Bake the Pastry Case: Preheat your oven to 200°C (180°C fan). On a lightly floured surface, roll out the chilled pastry until it's about 3mm thick and large enough to line a 23cm loose-bottomed tart tin. Carefully line the tin, pressing the pastry into the corners. Trim the excess. Prick the base with a fork, line with baking parchment, and fill with baking beans or uncooked rice. Bake for 15 minutes.

Finish the Pastry Case: Remove the paper and beans, then return the pastry case to the oven for another 5-7 minutes until it's pale golden and looks dry. Set aside to cool slightly while you make the filling. Reduce the oven temperature to 180°C (160°C fan). For more detailed guidance, blind baking is a fundamental technique worth mastering.

Prepare the Lemon Filling: In a heatproof bowl set over a saucepan of simmering water (a bain-marie), whisk together the lemon zest and juice, 200g caster sugar, softened butter, 4 egg yolks, and 2 whole eggs.

Cook the Filling: Continue to whisk gently and consistently over the low heat for about 10-12 minutes. The mixture will thicken to the consistency of custard. I find that using a silicone whisk helps prevent any scratching on the bowl. Once thickened, remove from the heat and pour the warm filling into the baked pastry case.

Whip the Meringue: In a spotlessly clean, grease-free bowl (I always give mine a wipe with a little lemon juice or vinegar), whisk the 4 egg whites with an electric mixer until they form soft peaks. Gradually add the 200g of caster sugar one tablespoon at a time, whisking continuously, until the meringue is thick, stiff, and glossy. Finally, whisk in the cornflour.

Top and Bake: Spoon the meringue over the lemon filling, ensuring it goes right to the pastry edge to create a seal. This helps prevent it from shrinking. Use the back of a spoon to create attractive swirls and peaks. Bake for 15-20 minutes, or until the meringue is golden brown and crisp on the outside.

Cool and Serve: Let the lemon pie cool completely in the tin before removing it. This is important as the filling needs time to set properly. Slice and serve at room temperature.